The present invention relates to a method for determining a work surface of a planar material in a surface treatment for obtaining a flat plate of a uniform thickness from a planar material, as well as to a machining method of such a work surface, a device for determining the foregoing work surface, and a flattening device.
A ceramic sintered plate such as a sputtering target or a metal plate prepared by metal rolling or forging, in most cases, is subject to be deformed by thermal stress or machining stress during the manufacturing process. Also the thickness is not uniform in some parts. In order to obtain a flat planar material of a uniform thickness from a planar material with such three-dimensional deformation, machining such as cutting, grinding, and electrical discharging is performed.
Conventionally, a material with this kind of deformation was subject to the foregoing processes by an operator setting such material directly on a processing machine, or the operator would roughly measure the deformation of the individual planar materials in advance with a straight end or the like, and insert a spacer during the stage of setting such materials in the processing machine in order to maintain flatness. Nevertheless, the current status is that the foregoing methods are conducted based on the operator's instincts.
For instance, when grinding a material based on the operator's instincts, even if the operator is an expert, he/she will need to perform such grinding more than necessary in order to obtain a plane. This is because it will not be possible to maintain the accuracy of flatness or uniform thickness without excessive grinding by the operator. Therefore, it was necessary to set the machining cost of the material itself higher, and this led to deterioration in the yield. In addition, this inevitably led to increased operation time of the processing machine.
As conventional technology, there are an apparatus to measure precisely the thickness of respective warped planar works (for instance, refer to Patent Document 1), a device to measure a warped planar works comprising a measurement reference unit, a measurement unit, a displacement measurement unit for converting into electrical signals, a warp measure display unit, and a control unit (for instance, refer to Patent Document 2), a manufacturing method of a ceramic product comprising the steps of pressurizing and molding ceramic material powder, irradiating a light beam on the surface thereof, and measuring the surface status upon receiving the reflected light (for instance, refer to Patent Document 3), a size measurement ceramic gauge provided with a stepwise portion (for instance, refer to Patent Document 4), a plate flatness measuring device comprising a downward measuring unit for measuring the flatness, a plate support pin, a vertical motion actuator, and a pressure regulation unit (for instance, refer to Patent Document 5), and a method for measuring the shape irregularity of a ceramic substrate using infrared thermography (for instance, refer to Patent Document 6).
Nevertheless, the foregoing conventional technologies are methods or devices for measuring flatness, measuring displacement or measuring shape irregularities, and do not provide the concept of improving the yield upon performing surface-machining such as cutting, grinding, and electrical discharging.    [Patent Document 1] Japanese Patent Laid-Open Publication No. H6-66549    [Patent Document 2] Japanese Examined Patent Application Publication No. S59-36202    [Patent Document 3] Japanese Patent Laid-Open Publication No. S63-173607    [Patent Document 4] Japanese Patent Laid-Open Publication No. H7-128002    [Patent Document 5] Japanese Patent No. 3418819    [Patent Document 6] Japanese Patent No. 3183935